Guaranteed Highest NAV

All Insurance companies launched ULIP plans with Guaranteed Highest NAV in the last 7 years.

I wonder how there can be a Guarantee in a market linked plan.

Even if you invest in Debt funds, you cant guarantee the Highest NAV of a particular period  on maturity.

So these funds will be managed in such a way that the NAV is not going beyond a level.

Is it worth investing in such plans.

Instead you may very well go for a 100% equity or for a balancer Plan which will give a better return over a period of 8 more years.